It is often desirable and frequently absolutely necessary to sample or test a portion of tissue from humans and even animals to aid in the diagnosis and treatment of patients with cancerous tumors, pre-malignant conditions and other diseases or disorders. Tumors are first noted in a patient by one of three ways, palpation, X-ray imaging or ultrasound imaging. Typically, in the case of cancer or the suspicion of malignant tumors, a very important process called tissue biopsy is performed to establish whether cells are cancerous.
Biopsy may be done by an open or closed technique. Open biopsy removes the entire tissue mass or a part of the tissue mass. Closed biopsy on the other hand is usually performed with a needle-like instrument and may be either an aspiration biopsy (hollow needle on a syringe) or a cored biopsy (special tissue cutting needle design). In needle aspiration biopsy, individual cells or clusters of cells are obtained for cytologic examination. In core biopsy, a segment of tissue is obtained for histologic examination which may be done as a frozen section or paraffin section.
The methods and procedures of obtaining tissue samples for cytologic or histologic examination have been performed historically by manual insertion and manipulation of the needle. These procedures are performed blind by the physician and guided by feel and known anatomic landmarks.
One prior art manual biopsy device includes a syringe arrangement including a stylet surrounded by a cannula. The stylet has a pointed tip and behind the tip a reduced diameter shank. The diameter of the pointed tip is slightly less than the internal diameter of the cannula such that the tip prevents tissue from entering the cannula as the cannula is passed through surrounding tissue to the point of intended biopsy. An O-ring is placed in sealing relationship between the reduced diameter shank and the internal diameter of the cannula. During operation of the biopsy syringe, the cannula is urged forward past the tip of the stylet in order to collect a tissue sample. As this occurs, a vacuum is formed in the cannula between the O-ring and the tissue sample. This vacuum tends to draw the tissue sample into the cannula.
This device, however, has disadvantages in that it is manual and thus does not give totally reliable results, as discussed below, in taking a biopsy of a very small tumor. Further, the vacuum created would be somewhat limited do the size of the cannula.
Examples of tissue harvesting devices have been described in U.S. Pat. Nos. 4,651,752; 4,702,260; and 4,243,048.
Two very important innovations in medical technology have influenced the field of tissue biopsy in the last five years. One is the use of tissue imaging devices which allow the physician to see inside the body and visually guide the needle to the tumor mass. The second is the invention of the Automatic Core Biopsy Device (ACBD). The ACBD is an instrument which propels a needle set with considerable force and speed in order to pierce the tumor mass and collect the tissue sample. This ACBD has allowed physicians to test tissue masses in the early stages of growth and has contributed to the medical trend of early diagnosis and successful treatment of cancer.
The Automated Core Biopsy Device allows a biopsy to be performed on tumor masses as small as two millimeters in diameter. This procedure is performed under ultrasound or X-ray guidance. Tumors of this size cannot be biopsied reliably by hand since the tumor is about the same size as the biopsy needle. Manual attempts at biopsy pushes the tumor away without piercing the mass. Automatic puncture devices accelerate the needle at such a velocity that even a small tumor can be pierced.
Automated Core Biopsy Devices (ACBD) use the True Cut needle set design. The True Cut needle is comprised of an inner notched stylet with an outer cannula. The stylet is advanced into the tissue under spring power followed by the cannula which cuts and traps the tissue sample in the notch of the stylet. The True Cut needle yields a core sample which is semi-circular in cross-section with a length determined by the stroke of the ACBD.
The stylet is a needle with a notched cut-out at the distal end. The cannula is a hollow needle with an angled cutting surface at the distal end which slides over the stylet. When the stylet is pushed into the tissue, the tissue is pierced and relaxes into the notched cut-out. When the cannula is slid forward, the tissue in the notch of the stylet is sliced off and retained in the notch until the cannula is drawn back.
The most common True Cut needle size used by ACBD's is 18 gage. The use of 18 gage needles is a compromise between the physician's desire to use the smallest, least invasive, needle gage and the pathologist's needs for as large a tissue sample as possible to minimize false-positive diagnosis. This compromise in needle size leads the physician to obtain multiple core samples from the biopsy site to allow the pathologist sufficient tissue for an accurate diagnosis.
The requirements of the physician and the pathologist dictate the need for an alternative approach in the function and design of the conventional ACBD and needle sets. The ideal product would allow the use of smaller needle gages and/or lessen the need for multiple samples to be taken from a given biopsy site.